Diastereoselective aldol reaction of 7-bromo-5-pyrido-1,4-benzodiazepin-2-one; Relative and absolute configuration of all stereoisomers

Majerić Elenkov, Maja; Žiher, Dinko; Višnjevac, Aleksandar; Hameršak, Zdenko; Kojić-Prodić, Biserka; Šunjić, Vitomir (2001) Diastereoselective aldol reaction of 7-bromo-5-pyrido-1,4-benzodiazepin-2-one; Relative and absolute configuration of all stereoisomers. Croatica Chemica Acta, 74 (3). pp. 707-724. ISSN 0011-1643

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Abstract

Aldol reaction of C(3) carbanion of 7-bromo-5-pyrido-1,4-benzodiazepin-2-one (1) with representative aliphatic and aromatic aldehydes and ketones afforded racemic mixtures syn/anti-7-bromo-3-(1 ' -hydroxy-1 ' -phenylmethyl)-1-methyl-5-(2 ' -pyridyl)-2,3-dihydro-1H-1,4-benzodiazepin-2-one (2/3), syn/anti-7-bromo-3-(1 ' -hydroxy-1 ' -phenylethyl)-1-methyl-5-(2 ' -pyridyl)-2,3-dihydro-1H-1,4-benzodiazepin-2-one (4/5) and syn/anti-7-bromo-3-(1 ' -hydroxy-2 ' -methylpropyl)-1-methyl-5-(2 ' -pyridyl)-2,3-dihydro-1H-1,4-benzodiazepin-2-one (6/7) with 60-85% diastereoselectivity. For prevailing diastereomeric racemates (+/-)-2 and (+/-)-4, syn relative configuration is deduced, whereas the prevailing diastereomer (+/-)-7 has anti configuration. Configurational assignment is based on H-1 NMR data and X-ray structure analysis, and the origin of inversion of diastereoselectivity is discussed. Racemic mixtures were separated on chiral HPLC column, and on the basis of the CD spectra (3R) absolute configuration was determined for (+)-enantiomers, and (3S) configuration for (-)-enantiomers. Consequently, (3R,1 'S) configuration is assigned to syn-(+)-enantiomers and (3R,1 'R)-configuration to anti(+)-enantiomers. In an attempt to use enantiomerically pure compounds 2-7 as catalysts in asymmetric alkylation of benzaldehyde by diethylzinc, these ligands proved chemically and configurationally unstable.

Item Type:	Article
Uncontrolled Keywords:	1,4-benzodiazepines; enantioseparation; HPLC chiral chromatography; relative and absolute configuration; circular-dichroism; conformation; 1,4-benzodiazepines; derivatives; complexes; acids
Subjects:	NATURAL SCIENCES > Chemistry
Divisions:	Division of Organic Chemistry and Biochemistry Division of Physical Chemistry
Projects:	Project title Project leader Project code Project type Struktura i svojstva (bio)molekula Biserka Kojić-Prodić 00980608 MZOS Steroselektivni katalitički i biokatalitički procesi Vitomir Šunjić 00980701 MZOS
Depositing User:	Maja Majerić Elenkov
Date Deposited:	19 Nov 2013 13:38
URI:	http://fulir.irb.hr/id/eprint/983

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